Human Respiratory Syncytial virus (RSV) is the leading cause of severe lower respiratory tract disease in infants and young children, and may repeatedly cause infection in the same individual. RSV also causes disease in immune-compromised adults and in the elderly. To date, there is no safe and effective vaccine against RSV and against other infective agents (virus, bacteria, etc.). Thus, there remains a need for vaccines against RSV and vaccines against other infective agents.